Comparison Of Emf Of Two Cells Using Potentiometer
Comparison Of Emf Of Two Cells Using Potentiometer — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Comparison of EMF of two cells using Potentiometer Used in experimental physics to compare the Electromotive Force (EMF) of two primary cells without drawing any current from them at the balance point. According to the principle of a potentiometer, the potential drop across a segment is proportional to its length: V = kl. At the null point, the EMF of the cell is balanced by the potential drop across the length l: E = kl. For the first cell: E1 = kl1. For the second cell: E2 = kl2. Divide the two equations to eliminate the potential gradient k: E1/E2 = l1/l2. The EMF of the driver cell must be greater than both E1 and E2. The positive terminals of all cells must be connected to the same point. The potentiometer wire must have a uniform cross-sectional area and resistance. Current through the potentiometer wire must remain constant during observations. Thinking that the cross-sectional area of the wire affects the ratio E1/E2; it does not, as long as it is uniform. Believing the length l depends on the internal resistance of the cells; at the null point, no current flows through the cell, so internal resistance does not affect the balance point.